Composite telephone and telegraph system



April 15, 1930.

H. NYQUIST ET AL COMPOSITE TELEPHONE AND TELEGRAPH SYSTEM Filed Sept ,4p/valuta;

INVENToRs Hgmlst ara/d ATTORNEYS.

.sund

Patented Apr. l5, 1

UNITED sTATEs-PATENT oFF-ica HARRY NYeUIs'r, or MILL-BURN, NEW JERSEY, Aim einem BRAND,- or BROOKLYN, lmw Yoan, Assienons 'ro AminicAn TELEPHONE Aim Tamiami; coinuimr,` A

COBPOMTIN 4OF YORK oourosrrn TELEPHONE AND TELEGBAPH SYSTEM .Application med september s, 192e. serial ne. 134,266.

This invention relates toa composite telephone and telegraph system and more plarticularly to a circuit arrangement byw ich a transmission line may be` availableI for tele- 5 phonic purposes at any time but will 'be in use for telegraphic purposes 'at other times.

In so-called composite'telephone and telegraph circuits, it has been a common practice to use a line simultaneously for both purposes by having' the two types of signals oc-v cupy -dlflerent parts vof the frequency spectrum. .In this invention, wepropose to use the relatively broad frequency band for both telephonic and ltelegraphic purposes, but it will be obvious that the two types of message cannot, inthatA case, .be transmitted simultaneously. However, in all lines set aside for telephonie purposes, there are periods. of greater or less durationwhen they are. idle and it is' the object of this invention to provide a circuit system by which the line 1s normally connected to Athe terminals 'of the telegr-aphic apparatus but is in condition to be connected to the terminals of the telephone apparatus whenever required for telephonie connection.' yBy this arrangement, there'lS 'supplied effectively a fulltime telephone clrcuit and a part time telegraphic service over the same circuit within the same`frequency range. This is a feature which is ofspecial importance if the line is onewhich provides a relatively small amount of ltelephone business.

Another object of our invention is to provide for this transfer from the one type of signaling tothe other" automatically on ar.-y rival of telephonie messages and this we accomplish by the use of voice o erated relalys which are effective to make an maintain 't e 40 telephonie connection during the necessary time butto restore the telegraphic connections onl the cessationjof the voice frequency currents in the telephone apparatus. Other objects of the invention will be seen from the following specification which, taken with the, accompanying drawing, illustrates certain 'ways of carrying out our 1nvention.

In the drawing, Figure 1 shows the c ircuital arrangement for one end of a four wire transmission system, the other end being description.

omitted forthe reason that it is identical in connection and in operation. In this ligure,- ythe `voice operated relay .for performing the operations mentioned above is used for this Vpurpose only. Fig. 2 is a modification of the circuit in Which-the desired operations arel controlled by voice operated relays normally intended to function as echo suppressors'and in -this case performing both functions. Fig.

3 is still a further modification showing thel use of a multiplex printing telegraph which carries with it certain requirements as to synchronous operation.

Inallof the figures, we have shown the in#` vention as applied to a four wire circuit in which the signals in one direction make Iuse of one pair of wires and those in the other only when and while the other party carries on the conversation. Inasmuch as the initiation of telegraph signals will go on independently of the use of the line fortelephonic purposes, it is necessary that storage facilie ties be provided by which telegraph mes-p sages may beaccumulated and later sent out r when the line becomes available', all ofwhich will appear more clearly from the following Referring particularl to Fig. 1, theres' shown one end of a signa ing system compris r ing the four-wire circuit made u 'of the pair L1 and the pair L2, the pair L1 being indicated for transmission of signalsto the remote-station and the pair L2 being indicated for rece 'tionvof signals from that station. The line 1' is normally connected by relay contacts I lO tov L the conductors 11 which latter are associated i` y with suitable telegraph transmitting apparatus.

While this apparatus may take on a, large variety of forms, we have' here shownl it as boing adapted for multiplex telegraphy by using 'a plurality of alternating currents of dierent frequencies distributed throughout the speech signaling band, which may be taken as extending from about 100 cyclesper.. second to 3000 cycles. It is quite pract1cal,. as is now well known in the art, to 'have'as many as or'20 telegraph channels dist .tributed Athroughout this range; Such tele- 4'graph signals, from suitable sources and `with suitable wave ilters,areind1cated as being impressed on the line 12 and arriving at a receivino' device 13 where the messag may be recordedin any suitable way for su .sequent transmission.' In this case',.the drawing indicates that the record would be made,

on a telegraphone wire and that retransmission occurs from the-transmitter' 14 which -eeds into the line 11. The operation of this transmitter 14 may be maintained by a motor l5 which in turn is controlled by suitable frelays to stop or start under the proper con ditions. f .l

Telegraph signals comingy in ,on the line L2 pass directly through contacts 18 to appropriate telegraph receiving ap aratus 19.v

`The connections thus far descri dare the ones normally existing and under these oo nditions telegraph messages may be transmity tedor received without special regard to other apparatus. However, in addition to the above there is vprovided the necessary 4telephone apparatus" to constitute the now wellknown four-wire telephone circuit. l consists of a local transmission line or sub- This scribers station 21 connected tof a hybrid coil 22, which hybrid coil has also connected withit the balancing network 23. The series winding of the hybrid coil 22 may pas's through a repeater- R1 from whence it continues over the line 24 throu h various piecesof apparatus to the termina s 26 of the relay 3 byf which it may be associated with the line L1. Bridged across the line 24 is the detector l D2 adapted upon the receiptof telephone currents to operate the relay 1 whichvin turn op.

crates the relays 2 and 3. The operation of the relay 3 transfers the line L1 from the telegraph transmitting apparatus to 4'the telephone transmittingl apparatus 'andthe operation of the relay 2 opens the circuit for the motor 15, whereupon the telegraph transmit'- ter 14 ceasesfto function. It will thus be seen that the one pair of wires L1 is connected for telephone transmission so far as the one endv Vof the line is concerned but. it will be borne in mind that at the other end of L1 there is associated telegraph receiving apparatus of the kind indicated by 19, thisreceiving apparatus being .maintained in connection with the line by contacts corresponding to the contacts 18. Itis necessary that piovision be made for normally 'maintaining the association of the telegraph receiving apparatus to the line but these means should'be such as to release or disconnect this apparatus as soon of operation, on closing this as the rela has been .operated Aand to connectthe te ephone receiving apparatus. To

this-end, we provide at the telegraph transmitting station a source of alternating cur-` rent of a frequencyl different vfrom that used in the telegraph'channels. In the figure, this .has been indicated as 3,000 cycles. Normally, this .3,000 cycle current passes overthe line and is received at the Vfurther end through a by-pass circuit comprising a band pass filter,

lillustrated here for this 3,000 cycle current,

and a detector D3, in the output circuit of which there is contained the relay 4. As long as this 3,000 cyclecurrent is on the line, the relay 4 will be excited to maintain vthe telegraph receiving apparatus 19 associated with the line but upon the operationvof relay 3,

this 3,000 cycle current ceases and immediately the relay 4 is released to connect the re- 'ceiving side of the telephone circuit to the line. This is shown clearl in the lower portion of Fig. 1, but it is to e understood that sol the description just given -relates to the corresponding apparatus at the further end of the line L1. `Thus, it is seen that an incoming.

voice current from the subscriber station 21 will automatically disconnect the telegraph transmitting and receiving apparatus from the line L1 and associate with it telephone apv paratus which will permit conversation in the one direction only.

A similar arrangement is used for the other side of the circuit so that telephone transmission may take place in the opposite direc- .known voice operated echo Suppressors of the kind described in patent to Mills, No. 1,434,790, dated November 7, 1922. Such 'an `echo su pressor ma consist of a detector D1 bridge across the ine v24 and a similar dethe detector D1 and operate the relay 5 to short-.circuit the line 34 and alsothe detector D1. They will also operate the relay 6- which in turn operates the relay 7 to remove a short circuit across the line 24, this short circuit being provided to prevent the well Yknown phenomenon of singing. Similarly, voice current coming in over the line L2 will pass into the detector D4 `and throughit operate the relay 8 to short-circuit the line 24 and the detector D1.

In connection with vsuch voice operated retector D4 bridged across the line 34. Voice currents coming'fro'm 21 will pass through lays, wherever they may occur, there will al- Ways be a certain delay and it is desirable that the transmission of the telephone signaling should be postponed suiiiciently to permit'the operation of these relays.- The delay devices for erforming this function take on a'variety of orms and they arehere indicated schematically only by P1, P2, P3 and P4.

. relay 7 of Fig. 1. It will benotedinconnection wlthFig. lthat In order that the relay 4 at the remote end of' line L1 shall not be operated by 3,000 cycle current emanating from the stat1on 21, therel is shown a low pass filter 29 with a cut-off at some suitable point Such as 2900 Ywhich will still permit the transmission of the essential i voice frequencies but will not permit the passage of a frequency to which therelay 4l is sensitive.

Fig. 2 is a circuit which is essentlally the same as Fig. 1 but in which the function of the detector D2 is performed byone-in the voice operated echo suppressor, in particular, the detector D1'.

lay 5 in the usual manner and at the same time will operate the relay 1 to perform the same function as the relay 1 of Fig. 1, it will be noted that at the same time this relay l, with 3, serves the same the operation ofthe echo Suppressors is quite independent of the remainder of the circuit and, if desired7 these may be omitted without effecting the circuit comprising our invention.

If it is desired to use the telegraph circuit described in Figs. 1 and 2 for multiplex printing telegraphy, the arrangement already described must be modified in order to maintain the synchroni of the distributors, for it is evident that in t e above arrangement, when the four-Wire circuit is used fortelephony, the synchronism of the multiplex system is interrupted and there is no assuraneethat when the circuit is again used for telegraphy, the

receivingdistributor will bein the correct position for the proper distribution of the received printer signals. This diliiculty is avoided by the arrangement of 3, 1n

which only those portions of the circuit are shown which are concerned with the modification. Instead of s nchronizingthe distriblutors, by means of t e received printer sig'- nals, as isl usual in the ordinary multiplex printing telegraph system, synchronism is here maintained over a separate channel outsideof the voice frequency range. This synchronizing channel, operating-at, say, 320.0v cycles, is bridged on the transmlttlng slde of the four-wirev circuit through the band pass filter F1 and on the receiving side of the four- Wire circuit through the band pass filter F2. A low pass filter F3' is used on the receiving side of the four-wire circuit sothat the synchronizing. current Willnot interfere with the telephone or telegraphcurrents. Thesend Upon receipt of telephone signals from 21, detector D1 will operate therepurpose-as relay 6, With absence of telephone currents.

ing distributor, by means of an added ring of segments, sends steady reversals to the sendin relay R1, 'tl1us transmitting 3200 cycle pu ses over the synchronizing channel to the receiving amplifier detector R2, these received pulses giving steady reversals'V tov the synchronizing line relay to which the correcting circuit 1s connected 1n the usual manner Thus synchronism of the printer signals is maintained regardless of the position of the switching relays 3 and 4 and of the use being made of the four-Wire circuit in the voice fre uency range.` i

hile this invention has been described specically in ,connection with a four-Wire line, it should be understood that it applies to any system using two two-way channels, such as a radio system with a transmitting and a receiving station at each terminal or to a twotwo-way system made up in part of four Wires and in part of radio channels and the expression four-channel transmission line is understood to cover any of these.l Whatis claimed is: 1. In a .signaling system comprising a transmission line, telegraph apparatus` associated -vvithl each end thereof, telephone apparatus adapted to be associated 'there- With,V and means` for automatically disconnecting the telegraphapparatus and connectin'gf'the'telephone apparatuson the arrivalof telephone currents and a special frequency signaling means at one end ofl the line tomaintain the telegraph `apparatus at the other end associated with the line during 2; In a signaling system comprisingja transmission line, telegraph apparatus' and v telephone apparatus adapted to be. associated With-each end thereof, means. for lnormally l maintaining the telegraph apparatus inassociation with said line, and means controlled by telephone currents to disconnect the telegraph apparatus and connect the telephone apparatus, and means associated `with the telegraph apparatus to store up telegraph message While the said apparatus is disconnected from the line.

3. Ina signaling systemv ycomprising atransmission line, telegraph apparatus and 3 graph transmitting apparatus and telephone I vwith each end thereof, a relay 'for normally maintaining the telegraph apparatus in association with said line, a voice-operatedrelay controlled by telephone 4currentsto disconnect the telegraph apparatus and connect the telephone apparatus, and means associated With the telegraph apparatus 'to stone up telegraph message while the said apparatus `is disconnected from the line. i

5. In a signaling system comprising a fourchannel transmission, line, signaling apparatus at one end ythereof` comprising telegraph transmitting apparatus and telephone transmitting apparatus adapted to be associated-with one pair of said channels and telegraph receiving apparatus and telephone receiving apparatus adapted to -beassociated i with the otherend'of said pair, means lfor paratus and connect the telephone apparatus.'l

' for automatically disconnecting1 normally maintaining the transmitting telegraph apparatus in association with .saidA pairs of" channels, meansV controlled by the transmitting telegraph apparatus to maintain the receivin telegraph apparatus as'- sociated with the ine during absence of telephone currents, and means controlled by telephon'e currents to disconnect the telegraph ap- '6. In a signaling system comprising a -four-Wire transmission line, signaling app'aratusl at one end ythereof comprising teletransmitting apparatus adapted to be 'associated with one pair of said wires, and telegraph receiving apparatus and telephone receiving apparatus adapted to be associated with the other end of said pair, and means the transmitting telegraph apparatusan connecting v ,the tele hone apparatus, l.said `means .being operate by voice currents and a special fre- 'quency signaling means at each end of the line to maintain the receiving telegraph apparatus at the other end associated with the line .during absence. of telephonecui'rents;

7. In a signaling'systein.comprising a fourwire transmission line, signalingapparatus at one `end thereofV comprising telegraph transmitting apparatus and telephone transmitting apparatus adapted to be associated .with one pair of said wires, and telegraph receiving apparatus and telephone receiving apparatus adapted to be associated with the other end of said pair, means for automatically disconnecting the telegraph apparatus and connecting the telephone apparatus,.said

rents, similar apparatus associated4 with theA rents.

the telegraph transmitting apparatus at each l n terminal to store'uptelegraph message while the said apparatus is disconnected from the line.

. 9. -In a signaling system comprising a transmission line, telegraph apparatus associated with each end thereof and adapted to signal in the telephone frequency range, telephone apparatus ada-pted to be associated with said line and means for automatically disconnecting the telegraph apparatus and connecting the telephone apparatus on arrival of telephone currents.

10. In. a signaling system comprising a transmission line, telegraph apparatus associated with each end thereof and adapted for.

multiplex telegraph signalingin the telephone frequency range, telephone a Yparatus adapted to"1beassociated Wirth the ine and .means for automatically disconnecting the telegraph apparatus andconnecting the telephone apparatus on arrival of telephone cur- 11. In. a signaling system comprising a transmission line, synchronous multiplex telegraph siglnalintg' apparatus associated with each end t ereo and adapted to signal in the telephone frequency range, telephone apparatus ada ted to be associated with the line and means' or disconnectingthe telegraph apparatus and connecting the telephone apparatus o n arrival of telephone currents, and a supplementary synchronizin signaling means operating outside the te e hone frequency range for maintaining sync ronisin between the telegraph transmittingapparatus and its corres ending receiving apparatus;

12. n a signaling system comprising a transmission line, the method l.of transmission of telegraph and telephone messages over the same channel and 1n the 'same frequency range, which consists in maintaining the telegraph apparatus normally inconnection with the line for transmission of telegraph signals in the tele hone frequency range, disconnect- 'ing the te egraph apparatus and connecting the telephone apparatus on the arrival. of the telephone current 'and by means of the telephone current, and maintaining said telephone connectiononly while telephone current is arriving. e

13. In a si aling system comprising a transmission line, the method of transmission of telegraph and. telephone messages over the same channel, which consists in maintaining thetelegraph apparatus normally in mis phone current and by means ofthe telephone current, maintaining said telephone connection only While telephone current is arriving, and storing up telegraph messages during the 5 use of the line for telephony. v

In testimony whereof, we have signed our names to this specification this 7 th day of September, 1926.

' HARRY NYQUIST.

SMART BRAND. 

